Explosive composition and process of production



July 19, 1938. H. A. LEWIS ET AL 2,124,201

EXPLOSIVE COMPOSITION AND PROCESS OF PRODUCTION Filed Sept. 15, 1934 ffALeu/is INVENTORS C. A. Woodbury ATTORNEY.

UNITED STATE Patented July 19, 1938 EXPLOSIVE COMPOSITION AND PROCESS OF PRODUCTION Application September 15, 1934, Serial No. 744,100 7 10 Claims. (01. 52-14) S PATENT OFFICE This invention relates to a new and'improved explosive composition and to a process for controlling the density thereof, said composition being characterized by relatively high density and a desirable and controllable degree of sensitiveness throughout.

Under certain conditions of use, relatively high density is a very desirable-property of explosives, since it allows a concentration of explosive strength within a smaller volume of borehole. This is particularly the case in hard rock blasting and in quarrying operations using well drill holes. Where high density is desired, gelatin dynamite has heretofore been the ideal explosive from the point of view of efiiciency. From an economical point of view, however, it has been the practice to replace gelatin dynamites, wherever possible, by other, lower cost explosives, particularly those having an ammonium nitrate base. Such ammonia dynamites, unfortunately do not have the desired high density of loading, particularly the economically favorable ones with a low nitroglycerin content. High density ammonium nitrate explosives can, of course, be produced by pressing or casting the charge, but such 'highly compressed compositions are in general too insensitive for satisfactory detonation with the usual blasting caps.

An object of our invention is an explosive composition of relatively high density and of high bulk strength. A-further. object is such an explosive characterized by a degree of sensitiveness throughout which is more completely controlled than is usually the case with such high density explosives. A further object is an ammonium nitrate explosive having the properties described herein. A still further object is a process for producing such explosives of controlled density and sensitiveness. Additional objects will be disclosed as the invention is described hereinafter.

We have found that the foregoing objects are accomplished when the explosive composition is produced by using therein a portion'of relatively high density pellets of explosive material with a mass of more readily detonatable explosive material, the latter material being in contact with the pellets, and wholly or substantially surrounding them. A principal advantage of this arrangement is that, by using high density pellets the average density of the entire composition is markedly increased while at the same time the sensitiveness of the combination, may be controlled to any desired degree.

Our invention is therefore applicable to various types of explosive compositions. It may comprise a chlorate or perchlorate explosive composition in compressed form such as to give a density higher than that of the remaining composition. Our high density component, however, preferably consists of a compressed explosive in pelleted or granular form, containing ammonium nitrate as the principal ingredient, together with a sufflcient-amount of sensitizing and oxygen balancing material so that the detonation wave communicated to these pellets by the surrounding explosive composition will be propagated throughout the mass. These pellets may be made solely of ammonium nitrate, but we preferably incorporate with the ammonium nitrate one or more of the carbon compounds to compensate for the position may be a gelatin dynamite, a semigelatinous dynamite,-an ammonium nitrate dynamite which is cap sensitive, or an explosive incapable of detonation by a commercial blasting cap but detonatable by a dynamite primer. Also when the pellets are chlorate explosives, the surrounding explosive is preferably a chlorate composition, in loose form, of lower density, or a lower degree of compression. It will be apparent from the foregoing that innumerable combinations will come within the scope of our invention.

While the most satisfactory procedure in bringing the pellets and the more readily detonatable portions of the explosives into suitable contact with one another will be to enclose the former within the latter material, for the purpose of our invention it is essential only that the pelleted material be contacted by the more readily detonatable material, so that the explosion, when once initiated, is propagated throughout the composition, the more sensitive explosive acting as the carrier of the detonating wave. Such extent of contact may be termed substantially surrounded" for the purpose of suitable definition.

In preparingan explosive according to this invention, in which the pelleted portion comprises an ammonium nitrate explosive, we find it satisfactory to use in such portion more than 50% am monium nitrate and preferably at least 85% of this compound. Various sensitizing materials may be utilized, that are capable of oxidation by ammonium nitrate, such as carbonaceous ingredients, inorganic metallic materials such as powdered aluminum, term-silicon or calcium silicide, aromatic nitrocompounds, or even small percentages of explosive compounds such as aliphatic nitric esters, ;nitroglycerin, ethylene glycol trate, nitrostarch, pentaerythritol tetranitrate and the like. Preferably, however, we employ nitrated aromatic hydrocarbons, for example dinitrotoluene or other nitrotoluene, together with a paramn hydrocarbon. A satisfactory composition has been found to consist of 92% aonium nitrate, t% dinitrotoluenc, and 4% paramn. The amounts of dlnitrotoluene and paraifin may be varied, preferably to include dinitrotoluene in amounts up to 20% and paramn up to amounts of 8%. Increasing the amoimt of dinltrotoluene gives an increased degree of sensitiveness to the composition, and still permits high densities. Decreasing this and increasing the paramn content, on the other hand, has the reverse effect. Cornpressed charges such as these will be too insensitive for detonation by means of a commercial blasting cap but will develop full blasting efiiciency when subjected to the detonating action of the surrounding, more sensitive explosive.

The pelleted compositions can be formed by any desired method, as for example by compressing or casting, and, while the density may vary over awide range, a suitable density may be between la and 1.5. The size of the pellets can also be varied widely as-desired, although for our purpose a satisfactory one may be of cylindrical form with a diameter of about A" and a length of Another method of forming the pellets is to compress the material to any predetermined density in the form of blocks or cakes, breaking these down, for example by means of cracking rolls, and passing the product over screens to obtain the desired size of pellets or grains.

An ammonium nitrate explosive containing a relatively small amount of nitroglycerin or other aliphatic liquid nitric ester as sensitizer is suitable for the more readily detonatable portion of the charge.- Satisfactory compositions for such use may be more fully illustrated by the following firmwares- Q mm Low g fi f Aminggoinis sensitiveynami go 11 n com gemtm p o sitlon N ltroglycerln l5. 18. 0 Nihmmi-f'nn 0.2 Ammonium nitrate 77 ll 66.0 Sodium niti'ate Soda 10. 0 carbonaceous combustitellel 3 .5

Examples l, 2 and 3 above, because of their compositions, are reay detonatable by the commercial blasting caps coonly used, and the composition of Example 4, in loose form, is more readily detonatable than the same composition in pelleted form, and can be detonated by a dynamite primer. The mimng of the two prc= portions to form the finished composition may be brought about in any desired way.

in the way of further illustrations of our mvention the following examples are given of actual mixings having suitable properties and which gave satisfactory performance. Blends containing respectively, 0, 20, and 40% ammonium nitrate pellets surrounded with a low density ammonia. dynamite containing nitroglycerin, 87% ammonium nitrate, 7.5% combustible material and 0.5'chalk. had the following densities:

Pellets I (percent) Similarly, a blend containing respectively, 0, 20, and 40% ammonium nitrate pellets surrounded with a low density ammonia dynamite containing 15% nitroglycerin, 77% ammonium nitrate, 7.5% combustibles and 0.5% chalk gave the following densities:

Pellets (percent) Density use pellets of ammonium nitrate only, we have found that our invention may be eficiently practicecl by including pellets of ammonium nitrate containing sensitizing materials in order to get rid of the excess oxygen that the ammonium nitrate contains.

Furtheore, the pellets contemplated by our invention may or may not be sumciently sensitive for detonation by means of a commercial blasting cap.

Our invention therefore in its broadest aspects contemplates an explosive charge which comprises a. multiplicity of individual charges of separate explosives, these being substantially surrounded by another explosive which has a higher degree of sensltiveness and which acts as a tie-- tonating agent for the individual charges.

The advantages of our invention, as described in the foregoing, will be readily apparent. The surrounding explosive portion is satisfactory for use from the point of view of sensitiveness in that any sensitiveness can be selected, and any other properties, such as varying degrees of water resistance, can be selected as desired. However, many of these types which may be selected are unsuitable and unsatisfactory for blasting in hard.

TOOL; because of their low density. This latter difiiculty is overcome by the pelleted composl= tion which imparts satisfactorily high density to the entire composition.

Preferably, we use the proportions by means of which maximum density increase is obtained. This maximum density may occur between 30% and of pelleted material. It will be apparent from the foregoing that the explosive properties, may be very conveniently controlled by varying the ratio of high density to the surrounding composition.

Heretofore it has been necessary, when high densities are required, to use gelatinous explosives, or high-content nitroglycerin explosives, which compositions are relatively expensive. The present invention for the first time enables compositions containing large amounts of ammonium nitrate and low percentages of nitroglycerin to replace those high density dynamites satisfactorily.

For the purpose of more fully illustrating one specific embodiment of our invention, reference may be made to the accompanying drawing in which the single figure shows a container A with a portion cut away to reveal one arrangement of the explosive pelletsB substantially surrounded by the more easily detonatable explosive material C. This embodiment of our invention is, however, to be taken as merely illustrative and not as limiting in any way the broad principles of our invention.

While we have described various modifications and embodiments of our invention in detail in the foregoing, it will be apparent therefrom that still further variations may be made in the method of procedure, in the size, shape and density of the less sensitive portion, and in the compositions used, within the scope and spirit of our invention. It is to be understood, therefore that we do not intend to be limited, except as indicated in the following patent claims:

We claim:

1. An explosive composition comprising an explosive matrix capable of sustaining propagation of the explosion upon initiation, and embedded in said matrix, aggregates comprising ammonium nitrate intermingled with an oxygen acceptor and compacted therewith to a density of at least 1.4.

2. An explosive composition comprising a matrix of a nitroglycerin explosive, and embedded in said matrix, aggregates comprising ammonium nitrate intermingled with an oxygen acceptor and compacted therewith to a density of at least 1.4.

3. An explosive composition comprising an explosive matrix capable of sustaining propagation of the explosion upon initiation, and embedded in said matrix, aggregates comprising more than 50% ammonium nitrate intermingled with a nitrotoluene and a paraflln hydrocarbon and compacted therewith to a density of at least 1.4.

4. An explosive composition comprising an explosive matrix capable of sustaining propagation of the explosive upon initiation, and embedded in said matrix, aggregates comprising more than 50% ammonium nitrate intermingled with 0.5-10.0% of a nitrotoluene and (LS-10.0% of a paraflin hydrocarbon and compacted therewith to a density of at least 1.4.

5. An explosive composition comprising a plurality of compact explosive aggregates embedded in an explosive matrix capable of initiation by means of a commercial blasting cap, said aggregates comprising ammonium nitrate intermingled with an oxygen acceptor and compacted therewith to a density of at least 1.4, said aggregates having in themselves a sensitiveness insfilcient to insure initiation by means of a commercial blasting cap.

6. The explosive composition of claim 5 wherein said oxygen acceptor comprises a mixture of a nitrotoluene and a paraflin hydrocarbon.

7. The explosive charge of claim 5 wherein said explosive matrix capable of initiation by means of a blasting cap comprises a nitroglycerin explosive.

8. The process of producing an explosive com-. position which comprises intimately mixing ammonium nitrate with an oxygen acceptor and compressing the resulting composition to form a pluralityof compact aggregates at the relatively high density of at least 1.4, and embedding said aggregates in an explosive matrix capable of sustaining propagation of the explosion upon initiation.

9. The process of producing an explosive composition which comprises intimately mixing ammonium nitrate with an oxygen acceptor and compressing the resulting composition to form a plurality of compact aggregates at the relatively high density of at least 1.4, said aggregates having a sensitiveness insufflcient to insure initiation by means of a commercial blasting cap, and embedding said aggregates in an explosive matrix capable of sustaining propagation of the explosion upon initiation.

10. The process of producing an explosive composition which comprises intirnately mixing ammonium nitrate with an oxygen acceptor and compressing the resulting composition to form a plurality of compact aggregates at the relatively high density of at least 1.4, and embedding said aggregates in an explosive matrix capable of ini- 55 tiation by means of a commercial blasting cap.

HAROLD A. LEWIS. CLIFFORD A. WOODBURY. 

